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Uniquely Managing Test Execution Resources using WebSockets

Executing tests for simple applications is complicated. You have to think about the users, how they interact with it, how those interactions propagate through different components, as well as how to handle error situations gracefully. But things get even more complicated when you start looking at more extensive systems, like those with multiple external dependencies.

Dependencies come in various forms, including third-party modules, cloud services, compute resources, networks, and others.

This level of complexity is standard in almost all projects involving a large organization, whether delivering internal tools or external products.

It means you must put emphasis on developing test systems and mechanisms good enough to validate not just code, but those third-party dependencies as well. After all, they’re part of the final product and failing to interact with them, means the product fails.

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Episode 3 - Decoupling Database Migrations at Application Startup

13 mins
  • Data models change and evolve with your application.
  • There’s plenty of tools that keep track of database schemas and automatically generate scripts to upgrade or downgrade them.
  • It’s common for developers to run a migration at the start of their app before running app code.
  • Our author explains two common problems with this approach.
    1. Modern day production deployments and horizontal scaling can get you into a race condition.
    2. You start assuming that new code will only ever run with the new schema.
  • You can decouple migrations from code changes by disabling parallelism during this time.
  • Make it a separate command or lock the database during the upgrade.
  • We can easily implement locking ourselves in any language.
    • Use Redis locks if you’re ok with something external to the DB.
    • Use the DB itself by writing to an extra table to say that you’re upgrading it.
  • Plan your deployment appropriately so you can run old code with new by making migrations additive in the short term.
  • Using a script at startup that optionally performs the migration based on an environment variable integrates wel with Docker and cloud services.
  • Upgrades of both code and data should be part of your testing BEFORE releasing to production.
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Episode 2 - Writing README files

13 mins
2020-01-26 documentation
  • What’s a README?
  • Modern day added formatting. Mostly Markdown, sometimes Restructured Text.
  • What to include in a README?
    • Name the project
    • Intro / Summary / Overview
    • Prerequisites
    • Installation instructions
    • Usage instructions
    • Contribution instructions.
    • Credit for important contributors.
    • Acknowledgments of projects you based yours on.
    • Ways to communicate with you or the community.
    • License information.
    • Project status information in the form of badges.
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Episode 0 - Introductions

3 mins
2020-01-12
Our first episode introducing the podcast. We’ll go over the motivation and what to expect of the coming episodes.

12 Trending Alternatives for Distributing Python Applications in 2020

One of the more prevalent topics in the Python ecosystem of 2019 was that of packaging and distribution. As the year comes to an end, I wanted to put together a summary of the many paths we currently have available to distribute apps built with Python. Though some of these also apply to any language.

Whether delivering an executable, a virtual environment, your packaged code, or a full application, the following list includes both standard systems and some up-and-comers to keep in mind as we enter 2020.

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Unconventional Secure and Asynchronous RESTful APIs using SSH

Some time ago, in a desperate search for asynchronicity, I came across a Python package that changed the way I look at remote interfaces: AsyncSSH.

Reading through their documentation and example code, you’ll find an interesting assortment of use cases. All of which take advantage of the authentication and encryption capabilities of SSH, while using Python’s asyncio to handle asynchronous communications.

Thinking about various applications I’ve developed over the years, many included functions that could benefit from decoupling into separate services. But at times, I would avoid it due to security implications.

I wanted to build informative dashboards that optimize maintenance tasks. But they bypassed business logic, so I wouldn’t dare expose them over the same interfaces. I even looked at using HTTPS client certs, but support from REST frameworks seemed limited.

I realized that asyncssh could provide the extra security I was looking for over a well known key-based system. And in my never-ending quest to find what makes things tick, I decided to take a stab at writing a REST-ish service over SSH.

A great way to familiarize myself with the library and the protocol, it helped me learn more about building asynchronous apps, creating a small framework called korv.

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Practical Log Viewers with Sanic and Elasticsearch - Designing CI/CD Systems

One of the critical pieces in a build system is the ability to view build and test output. Not only does it track progress as the build transitions through the various phases, it’s also an instrument for debugging.

This chapter in the continuous builds series covers how to build a simple log viewer. You’ll find details on retrieving log entries from Docker containers, serving them through Python, linking from a GitHub pull request, and highlighting the data for easy reading.

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Painless Status Reporting in GitHub Pull Requests - Designing CI/CD Systems

Continuing the build service discussion from the Designing CI/CD Systems series, we’re now at a good point to look at reporting status as code passes through the system.

At the very minimum, you want to communicate build results to our users, but it’s worth examining other steps in the process that also provide useful information.

The code for reporting status isn’t a major feat. However, using it to enforce build workflows can get complicated when implemented from scratch.

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Command Execution Tricks with Subprocess - Designing CI/CD Systems

The most crucial step in any continuous integration process is the one that executes build instructions and tests their output. There’s an infinite number of ways to implement this step ranging from a simple shell script to a complex task system.

Keeping with the principles of simplicity and practicality, today we’ll look at continuing the series on Designing CI/CD Systems with our implementation of the execution script.

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Conveying Build and Test Information with Repository Badges

When you check out a repository on github, sometimes theres a little bit of flare at the top of the project that catches your eye. This bit of flare is called a badge and can be used to indicate build status, test coverage, documentation generation status, version support, software compatibilty statements or even community links to gitter or discord where you can find more help with the project. I used to think that badges were fancy fluff people added to their projects to make them seem more professional. Continue reading

Easy Clustering with Docker Swarm - Designing CI/CD Systems

Building code is sometimes as simple as executing a script. But a full-featured build system requires a lot more supporting infrastructure to handle multiple build requests at the same time, manage compute resources, distribute artifacts, etc. After our last chapter discussing build events, this next iteration in the CI/CD design series covers how to spin-up a container inside Docker Swarm to run a build and test it. What is Docker Swarm When running the Docker engine in Swarm mode your effectively creating a cluster. Continue reading

Awesome Webhook Handling with Sanic - Designing CI/CD Systems

After covering how to design a build pipeline and define build directives in the continuous builds series, it’s time to look at handling events from a code repository.

As internet standards evolved over the years, the HTTP protocol has become more prevalent. It’s easier to route, simpler to implement and even more reliable. This ubiquity makes it easier for applications that traverse or live on the public internet to communicate with each other. As a result of this, the idea of webhooks came to be as an “event-over-http” mechanism.

With GitHub as the repository management platform, we have the advantage of using their webhook system to communicate user actions over the internet and into our build pipeline.

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4 Attempts at Packaging Python as an Executable

A few years back I researched how to create a single-file executable of a Python application. Back then, the goal was to make a desktop interface that included other files and binaries in one bundle. Using PyInstaller I built a single binary file that could execute across platforms and looked just like any other application.

Fast forward until today and I have a similar need, but a different use case. I want to run Python code inside a Docker container, but the container image cannot require a Python installation.

Instead of blindly repeating what I tried last time, I decided to investigate more alternatives and discuss them here.

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Effortless Parsing of Build Specifications - Designing CI/CD Systems

Every code repository is different. The execution environment, the framework, the deliverables, or even the linters, all need some sort of customization. Creating a flexible build system requires a mechanism that specifies the steps to follow at different stages of a pipeline.

As the next chapter in the Comprehensive CI/CD Pipeline and System Design series, this article examines which instructions you’ll want to convey to your custom system and how to parse them. The focus is around a common solution, adding a file into the repository’s root directory that’s read by your execution engine when receiving new webhooks.

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Best Tips for Running Enterprise CI/CD in the Cloud

There are many solutions to building code, some of them are available as cloud services, others run on your own infrastructure, on private clouds or all of the above. They make it easy to create custom pipelines, as well as simple testing and packaging solutions. Some even offer open source feature-limited “community editions” to download and run on-premises for free.

Following is my experience on the important aspects to consider when deciding on a build system for your organization that depends on cloud services. The original intent was to include a detailed review of various online solutions, but I decided to leave that for another time. Instead, I’m speaking more from an enterprise viewpoint, which is closer to reality in a large organization than the usual how-to’s. We’re here to discuss the implications and the practicality of doing so.

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